Pultrusion is a technique in which longitudinally continuous fibrous structures are used to pull a resin through a die so that the resin sets and produces a rigid part downstream of the die to which the pulling force is applied.
Originally the longitudinal fibres consisted of simply longitudinal in the extending rovings and the parts were of a relatively simple cross section such as rods, T-bars and the like. However developments have been introduced to reduce the wall thickness of the parts so that complex cross sections including hollow cross sections could be manufactured. In order to achieve the necessary strength of the parts, it was necessary to introduce transverse fibers to provide strength in the transverse direction. Such transverse fibers are conventionally applied using a mat of a woven or non woven material. In many cases the fibers in the mat are generally random so that the number of fibers extending in the transverse direction is relatively small. One major problem with the mat is that it is relatively expensive and can be very expensive so that it is more than double per pound of the cost of the simple conventional rovings. One direction of development has been to provide improved mats which apply more of the fibers in the transverse direction thus allowing the mat to be of reduced thickness to provide the required strength or toughness in the finished part. An example of a mat tailored for pultrusion is shown in published International application PCT/WO78529A1 published 28 Dec. 2000 and assigned to Pella.
An alternative approach to the expense of the mat is to attempt to attach to the longitudinal rovings some transverse fibers which are simply chopped roving material. One example of an arrangement of this type is shown in U.S. Pat. No. 5,324,377 of the present inventor Davies. This method of pultrusion attempted to attach transverse fibers to the outside of a body of longitudinal rovings so as to be carried through the die with the rovings. This method has to date not achieved commercial success.
In order to minimize material costs, commercial pultrusion is normally carried out using polyester as the resin which is a simple thermo-set resin material so that it can be applied to the fibers from a bath and is thermo-set within the heated die. However other resins can be used.
Mats for reinforcing pultruded parts are provided to add structural strength and in order to provide the required or expected amount of strength have a weight of fibers greater than 0.5 ounces per square foot and generally 0.75 to 1.0 ounces per square foot
Veils, which are used to provide surface characteristics and not to provide any structural strength are lighter, generally less than 0.5 ounces per square foot and typically of the order of 0.1 ounces per square foot. Conventional veils are used outside rovings or outside mats at the surface to increase the amount of resin located outside the mat and locate generally finer fibers at the surface to provide an improved surface appearance or to retain the stiffer glass fibers within the resin to prevent fiber “bloom” or projecting fibers which can act as slivers. This latter requirement to prevent slivers is particularly important in tool handles or similar products. The retention of fibers to prevent weathering or bloom is particularly important in fenestration or similar products. Veils are well known and well used, when required for the part concerned, by persons skilled in this art and are not intended to form part of and are not considered as part of the fiber reinforcement.
In U.S. Pat. No. 6,746,747 (Davies) of the present Applicants issued Jun. 8, 2004 is disclosed using a resin which can include non-linear resins such as urethane or polyester material and reinforcing fiber layers including at least one first layer of fibers having fibers extending only in the longitudinal pultrusion direction and one or more second layers, where the second layer consist of a pre-formed mat or veil having a total quantity of fibers in the layer which is of the order of or less than 0.5 ounces per square foot. The mat layer can be located in the pultruded wall so that it is on the inside surface of a hollow or in a central position between two layers of unidirectional rovings. The disclosure of the above Davies patent is incorporated herein by reference to provide details of pultrusion methods.
Curtain wall is a term used to describe a building façade which does not carry any dead load from the building other than its own dead load. These loads are transferred to the main building structure through connections at floors or columns of the building. A curtain wall is designed to resist air and water infiltration, wind forces acting on the building, seismic forces (usually only those imposed by the inertia of the curtain wall), and its own dead load forces.
Curtain walls differ from storefront systems in that they are designed to span multiple floors, and take into consideration design requirements such as: thermal expansion and contraction; building sway and movement; water diversion; and thermal efficiency for cost-effective heating, cooling, and lighting in the building.
The first curtain walls were made with steel mullions, and the plate glass was attached to the mullions with asbestos or fiberglass modified glazing compound. Later silicone sealants or glazing tape were substituted. Some designs included an outer cap to hold the glass in place and to protect the integrity of the seals. The 1970's began the widespread use of aluminum extrusions for mullions. Aluminum offers the unique advantage of being able to be easily extruded into nearly any shape required for design and aesthetic purposes.
Similarly, sealing methods and types have evolved over the years, and as a result, today's curtain walls are high performance systems which require little maintenance.
In addition to providing an aesthetic appearance for the sides of a modern multi-story building, some of the major performance objectives of a curtain wall system of supported panels are as follows:
to provide a barrier or at least resistance to excessive amounts of exterior air infiltrating around the edges of panels into one or more interior environments within the building;
to provide a barrier or at least resistance to excessive amounts of exterior rain or other exterior liquids/particles infiltrating around the panel edges into one or more interior spaces within the building, typically when the liquids or particles tend to infiltrate in conjunction with air infiltration;
to provide a coefficient of expansion which is close to that of glass so as to reduce or remove the necessity to provide the expansion joints which are necessary with aluminum bearing in mind that the frame members can span several floors of a building.
to provide resistance to structural loads, specifically including supporting the weight of the panels and resisting seismic loads, wind loads, and thermal expansion/contraction loads, if any; and
to provide a thermal barrier or at least resistance to excessive heat transfer between the exterior air and one or more interior environments.
Typically therefore current frame members for the curtains walls are manufactured of extruded aluminum. This can be coated with a paint or can be simply anodized to provide a suitable finish. The frame members are typically rectangular in cross section with an inner wall and side walls inside the outer sheathing of the building and the outer sheathing attached to an outer mounting portion of the frame member
However aluminum has many disadvantages in that it is susceptible to scratching and marring whether anodized or painted, it has high heat conductivity and its coefficient of thermal expansion is very different from that of glass.